This invention relates to laminated components of the open magnetic circuit type.
Antenna coils and other similar components must have open magnetic circuit structures so that they can detect each external electromagnetic field or cause electromagnetic coupling through interlinkage with the field. Inductors of the open magnetic circuit type are made by winding a conductor coil on a ferrite rod or the like of high permeability. The products are large in size and present fabrication problems including complexity of the process. Recently, inductors that depend on the lamination technique for the fabrication have come to notice in the art. The laminated inductors are built up, for instance, by superposing, by turns, magnetic layers of ferrite powder paste and fragmentary coil-forming conductor patterns and then sintering the laminate at elevated temperature. In the laminated inductors of the structure described, the conductor patterns are embedded in the sintered magnetic body and the magnetic circuit involved is virtually closed. Then, it may appear possible to convert it into an open magnetic circuit by providing a nonmagnetic layer of alumina or the like around the superposed magnetic layers, with conductor patterns printed along the border regions between the magnetic and nonmagnetic layers, and thereafter sintering the resulting laminate structure. Attempts for trial fabrication in this way have, however, revealed great complicacy of the process steps and resulted in defects, such as deformations, strains, and cracks, and also ununiformity of quality. This is partly because precise register of the magnetic and nonmagnetic layers is impossible and also because the two material layers shrink differently on sintering.